fallrain / ics-pa-notes.md

+++ date = '2025-02-15T16:55:11+08:00' draft = true title = 'NJU ICS PA Notes' +++ One may encounter some hurdles here and there when drilling through [NJU ICS PA 2024](https://nju-projectn.github.io/ics-pa-gitbook/ics2024/), which is surely a very good educational project btw. So here's my two cents. ## Makefiles Spaghetti - `Q := @`: The `@` symbol in a Makefile is used to suppress the command echoing. When `Q` is used before a command, it prevents the command from being printed to the terminal before execution. - In a Makefile, `:=` and `=` are used to define variables, but they behave differently: - `=` (Recursive or Lazy Assignment): The value is expanded when the variable is used, not when it is defined. - `:=` (Simple or Immediate Assignment): The value is expanded immediately when the variable is defined. - `::` is a double colon rule, which allows multiple rules for the same target. Each rule is treated independently. Makefile for compile menuconfig is at `nemu/scripts/config.mk`. All the source file names are gathered from `filelist.mk` under `nemu/src`. ```makefile # Include all filelist.mk to merge file lists FILELIST_MK = $(shell find -L ./src -name "filelist.mk") include $(FILELIST_MK) ``` And all `.c` files under `DIRS-y` will be added to `SRCS-y`. ```makefile SRCS-y += $(shell find -L $(DIRS-y) -name "*.c") ``` NEMU Compilation happens at `nemu/scripts/build.mk`. ```makefile OBJS = $(SRCS:%.c=$(OBJ_DIR)/%.o) $(CXXSRC:%.cc=$(OBJ_DIR)/%.o) # Compilation patterns $(OBJ_DIR)/%.o: %.c @echo + CC $< @mkdir -p $(dir $@) @$(CC) $(CFLAGS) -c -o $@ $< $(call call_fixdep, $(@:.o=.d), $@) $(OBJ_DIR)/%.o: %.cc @echo + CXX $< @mkdir -p $(dir $@) @$(CXX) $(CFLAGS) $(CXXFLAGS) -c -o $@ $< $(call call_fixdep, $(@:.o=.d), $@) ``` Which is included by `nemu/scripts/native.mk` along with target `run` and `gdb` etc.